Supply Cases behave essentially the same way as Chests and spawn alongside them at predetermined locations throughout the Trial Grounds, when facing The Nemesis.
They only contain one specific Item, the Vaccine , which is used to cure one's self from T-Virus Contamination.
By default, a Trial will spawn 4 Supply Cases, just enough so that each Survivor can theoretically be cured once.
Supply Cases are much quicker to open than regular Chests, taking only 4 seconds to do so.
However, unlike Chests, a Supply Case does not stay open and will automatically close itself after 15 seconds, if the Vaccine is not retrieved from it.